1. Field
The present disclosure relates generally to aircraft and in particular to a method and apparatus for aircraft structural systems. Still more particularly, the present disclosure relates to a method and apparatus for a rib structure and attachment system for composite wing panels.
2. Background
In aircraft structures, wing panels, which consist of skins and stringers, may react to wing bending loads. These loads and the resulting deflections may produce upper wing compression buckling and a crushing load on ribs supporting the wing panels. The compression buckling capability for the panel may be driven by geometry, rib spacing and stringer spacing. The boundary conditions for the panel are determined by the method of support the rib gives the skin/stringer.
Traditional aluminum panel design as shown in FIG. 1 may provide panel support by attaching rib 10 to stringers 12 by means of a series of rib bolts 14 between free flange 16 of stringers 12 and associated rib chord flange 18. Skins 20 may be attached to the stringer outer flanges 22 using fasteners. An alternative method may be to attach a butterfly clip between the stringer web and the rib chord (not shown). These attachments may provide column stability for the panel and may not let the stringer roll over. These designs may be undesirable because they require installation while the wing box is being built. Drilling holes inside an enclosed wing box may present many challenges.
Further, application of this rib bolt design to a composite wing structure may create interlaminar tension problems in the stringer radius. This configuration may provide a poor load path for composite structure, which may require reinforcement methods for the stringer radius, adding more cost. The composite wing also may need disbond arrestment fasteners common to the stringer and skin in addition to the rib to stringer attachment.
It is therefore desirable to provide structural elements that provide an improved load path for rib support of wing panels. It is further desirable that the structure not require drilling of holes inside an enclosed wing box.